using System;

using NBitcoin.BouncyCastle.Crypto.Utilities;
using NBitcoin.BouncyCastle.Utilities;

namespace NBitcoin.BouncyCastle.Crypto.Digests
{
	/**
    * Base class for SHA-384 and SHA-512.
    */
	internal abstract class LongDigest
		: IDigest, IMemoable
	{
		private int MyByteLength = 128;

		private byte[] xBuf;
		private int xBufOff;

		private long byteCount1;
		private long byteCount2;

		internal ulong H1, H2, H3, H4, H5, H6, H7, H8;

		private ulong[] W = new ulong[80];
		private int wOff;

		/**
        * Constructor for variable length word
        */
		internal LongDigest()
		{
			xBuf = new byte[8];

			Reset();
		}

		/**
        * Copy constructor.  We are using copy constructors in place
        * of the object.Clone() interface as this interface is not
        * supported by J2ME.
        */
		internal LongDigest(
			LongDigest t)
		{
			xBuf = new byte[t.xBuf.Length];

			CopyIn(t);
		}

		protected void CopyIn(LongDigest t)
		{
			Array.Copy(t.xBuf, 0, xBuf, 0, t.xBuf.Length);

			xBufOff = t.xBufOff;
			byteCount1 = t.byteCount1;
			byteCount2 = t.byteCount2;

			H1 = t.H1;
			H2 = t.H2;
			H3 = t.H3;
			H4 = t.H4;
			H5 = t.H5;
			H6 = t.H6;
			H7 = t.H7;
			H8 = t.H8;

			Array.Copy(t.W, 0, W, 0, t.W.Length);
			wOff = t.wOff;
		}

		public void Update(
			byte input)
		{
			xBuf[xBufOff++] = input;

			if (xBufOff == xBuf.Length)
			{
				ProcessWord(xBuf, 0);
				xBufOff = 0;
			}

			byteCount1++;
		}

		public void BlockUpdate(
			byte[] input,
			int inOff,
			int length)
		{
			//
			// fill the current word
			//
			while ((xBufOff != 0) && (length > 0))
			{
				Update(input[inOff]);

				inOff++;
				length--;
			}

			//
			// process whole words.
			//
			while (length > xBuf.Length)
			{
				ProcessWord(input, inOff);

				inOff += xBuf.Length;
				length -= xBuf.Length;
				byteCount1 += xBuf.Length;
			}

			//
			// load in the remainder.
			//
			while (length > 0)
			{
				Update(input[inOff]);

				inOff++;
				length--;
			}
		}

		public void Finish()
		{
			AdjustByteCounts();

			long lowBitLength = byteCount1 << 3;
			long hiBitLength = byteCount2;

			//
			// add the pad bytes.
			//
			Update((byte)128);

			while (xBufOff != 0)
			{
				Update((byte)0);
			}

			ProcessLength(lowBitLength, hiBitLength);

			ProcessBlock();
		}

		public virtual void Reset()
		{
			byteCount1 = 0;
			byteCount2 = 0;

			xBufOff = 0;
			for (int i = 0; i < xBuf.Length; i++)
			{
				xBuf[i] = 0;
			}

			wOff = 0;
			Array.Clear(W, 0, W.Length);
		}

		internal void ProcessWord(
			byte[] input,
			int inOff)
		{
			W[wOff] = Pack.BE_To_UInt64(input, inOff);

			if (++wOff == 16)
			{
				ProcessBlock();
			}
		}

		/**
        * adjust the byte counts so that byteCount2 represents the
        * upper long (less 3 bits) word of the byte count.
        */
		private void AdjustByteCounts()
		{
			if (byteCount1 > 0x1fffffffffffffffL)
			{
				byteCount2 += (long)((ulong)byteCount1 >> 61);
				byteCount1 &= 0x1fffffffffffffffL;
			}
		}

		internal void ProcessLength(
			long lowW,
			long hiW)
		{
			if (wOff > 14)
			{
				ProcessBlock();
			}

			W[14] = (ulong)hiW;
			W[15] = (ulong)lowW;
		}

		internal void ProcessBlock()
		{
			AdjustByteCounts();

			//
			// expand 16 word block into 80 word blocks.
			//
			for (int ti = 16; ti <= 79; ++ti)
			{
				W[ti] = Sigma1(W[ti - 2]) + W[ti - 7] + Sigma0(W[ti - 15]) + W[ti - 16];
			}

			//
			// set up working variables.
			//
			ulong a = H1;
			ulong b = H2;
			ulong c = H3;
			ulong d = H4;
			ulong e = H5;
			ulong f = H6;
			ulong g = H7;
			ulong h = H8;

			int t = 0;
			for (int i = 0; i < 10; i++)
			{
				// t = 8 * i
				h += Sum1(e) + Ch(e, f, g) + K[t] + W[t++];
				d += h;
				h += Sum0(a) + Maj(a, b, c);

				// t = 8 * i + 1
				g += Sum1(d) + Ch(d, e, f) + K[t] + W[t++];
				c += g;
				g += Sum0(h) + Maj(h, a, b);

				// t = 8 * i + 2
				f += Sum1(c) + Ch(c, d, e) + K[t] + W[t++];
				b += f;
				f += Sum0(g) + Maj(g, h, a);

				// t = 8 * i + 3
				e += Sum1(b) + Ch(b, c, d) + K[t] + W[t++];
				a += e;
				e += Sum0(f) + Maj(f, g, h);

				// t = 8 * i + 4
				d += Sum1(a) + Ch(a, b, c) + K[t] + W[t++];
				h += d;
				d += Sum0(e) + Maj(e, f, g);

				// t = 8 * i + 5
				c += Sum1(h) + Ch(h, a, b) + K[t] + W[t++];
				g += c;
				c += Sum0(d) + Maj(d, e, f);

				// t = 8 * i + 6
				b += Sum1(g) + Ch(g, h, a) + K[t] + W[t++];
				f += b;
				b += Sum0(c) + Maj(c, d, e);

				// t = 8 * i + 7
				a += Sum1(f) + Ch(f, g, h) + K[t] + W[t++];
				e += a;
				a += Sum0(b) + Maj(b, c, d);
			}

			H1 += a;
			H2 += b;
			H3 += c;
			H4 += d;
			H5 += e;
			H6 += f;
			H7 += g;
			H8 += h;

			//
			// reset the offset and clean out the word buffer.
			//
			wOff = 0;
			Array.Clear(W, 0, 16);
		}

		/* SHA-384 and SHA-512 functions (as for SHA-256 but for longs) */
		private static ulong Ch(ulong x, ulong y, ulong z)
		{
			return (x & y) ^ (~x & z);
		}

		private static ulong Maj(ulong x, ulong y, ulong z)
		{
			return (x & y) ^ (x & z) ^ (y & z);
		}

		private static ulong Sum0(ulong x)
		{
			return ((x << 36) | (x >> 28)) ^ ((x << 30) | (x >> 34)) ^ ((x << 25) | (x >> 39));
		}

		private static ulong Sum1(ulong x)
		{
			return ((x << 50) | (x >> 14)) ^ ((x << 46) | (x >> 18)) ^ ((x << 23) | (x >> 41));
		}

		private static ulong Sigma0(ulong x)
		{
			return ((x << 63) | (x >> 1)) ^ ((x << 56) | (x >> 8)) ^ (x >> 7);
		}

		private static ulong Sigma1(ulong x)
		{
			return ((x << 45) | (x >> 19)) ^ ((x << 3) | (x >> 61)) ^ (x >> 6);
		}

		/* SHA-384 and SHA-512 Constants
         * (represent the first 64 bits of the fractional parts of the
         * cube roots of the first sixty-four prime numbers)
         */
		internal static readonly ulong[] K =
		{
			0x428a2f98d728ae22, 0x7137449123ef65cd, 0xb5c0fbcfec4d3b2f, 0xe9b5dba58189dbbc,
			0x3956c25bf348b538, 0x59f111f1b605d019, 0x923f82a4af194f9b, 0xab1c5ed5da6d8118,
			0xd807aa98a3030242, 0x12835b0145706fbe, 0x243185be4ee4b28c, 0x550c7dc3d5ffb4e2,
			0x72be5d74f27b896f, 0x80deb1fe3b1696b1, 0x9bdc06a725c71235, 0xc19bf174cf692694,
			0xe49b69c19ef14ad2, 0xefbe4786384f25e3, 0x0fc19dc68b8cd5b5, 0x240ca1cc77ac9c65,
			0x2de92c6f592b0275, 0x4a7484aa6ea6e483, 0x5cb0a9dcbd41fbd4, 0x76f988da831153b5,
			0x983e5152ee66dfab, 0xa831c66d2db43210, 0xb00327c898fb213f, 0xbf597fc7beef0ee4,
			0xc6e00bf33da88fc2, 0xd5a79147930aa725, 0x06ca6351e003826f, 0x142929670a0e6e70,
			0x27b70a8546d22ffc, 0x2e1b21385c26c926, 0x4d2c6dfc5ac42aed, 0x53380d139d95b3df,
			0x650a73548baf63de, 0x766a0abb3c77b2a8, 0x81c2c92e47edaee6, 0x92722c851482353b,
			0xa2bfe8a14cf10364, 0xa81a664bbc423001, 0xc24b8b70d0f89791, 0xc76c51a30654be30,
			0xd192e819d6ef5218, 0xd69906245565a910, 0xf40e35855771202a, 0x106aa07032bbd1b8,
			0x19a4c116b8d2d0c8, 0x1e376c085141ab53, 0x2748774cdf8eeb99, 0x34b0bcb5e19b48a8,
			0x391c0cb3c5c95a63, 0x4ed8aa4ae3418acb, 0x5b9cca4f7763e373, 0x682e6ff3d6b2b8a3,
			0x748f82ee5defb2fc, 0x78a5636f43172f60, 0x84c87814a1f0ab72, 0x8cc702081a6439ec,
			0x90befffa23631e28, 0xa4506cebde82bde9, 0xbef9a3f7b2c67915, 0xc67178f2e372532b,
			0xca273eceea26619c, 0xd186b8c721c0c207, 0xeada7dd6cde0eb1e, 0xf57d4f7fee6ed178,
			0x06f067aa72176fba, 0x0a637dc5a2c898a6, 0x113f9804bef90dae, 0x1b710b35131c471b,
			0x28db77f523047d84, 0x32caab7b40c72493, 0x3c9ebe0a15c9bebc, 0x431d67c49c100d4c,
			0x4cc5d4becb3e42b6, 0x597f299cfc657e2a, 0x5fcb6fab3ad6faec, 0x6c44198c4a475817
		};

		public int GetByteLength()
		{
			return MyByteLength;
		}

		public abstract string AlgorithmName
		{
			get;
		}
		public abstract int GetDigestSize();
		public abstract int DoFinal(byte[] output, int outOff);
		public abstract IMemoable Copy();
		public abstract void Reset(IMemoable t);
	}
}
